/ Dictionary / Index T tacho-: Meaning and Definition of Find definitions for: tacho- Pronunciation: [key] a combining form meaning “speed,” used in the formation of compound words:Cf. tachometer. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. tachistoscope tachogram Related Content Daily Word Quiz: ravenous Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language